Vehicles that include all-wheel drive capability have many advantages over vehicles that are driven using a single axle. Specifically, vehicles that include all-wheel drive capability have increased traction and enhanced drivability over similar vehicles that are driven using a single axle. All-wheel drive vehicles, however, do have some disadvantages.
Drivelines of all-wheel drive vehicles typically include many more moving components than a driveline of a vehicle having a single drive axle. Moving these components requires additional power, so all-wheel drive vehicles tend to have a fuel economy that is lower than that of vehicles having a single drive axle. This is particularly true when the all-wheel drive vehicle is operated in a manner that does not disconnect a second drive axle from a remaining portion of the driveline.
To improve the fuel economy of all-wheel drive vehicles, vehicle manufacturers have incorporated active differentials into the driveline. A control system in communication with the active differential is used to engage partially engage, or disengage the differential. In addition to disengaging the second drive axle from a remaining portion of the driveline, active differentials provide the benefit of being able to control an amount of torque applied to the second drive axle or a portion of the second drive axle.
Actuation systems typically used with active differentials typically comprise an actuation motor, a force translational device, and a clutch pack. Through the force translational device, force applied by the actuation motor is applied to the clutch pack, at least variably engaging two components of the driveline. The amount of force needed to engage the clutch pack can vary as the actuation system wears. Current systems, however, apply the same electrical current to the actuation motor, which applies the same force in all situations. It would be better to accurately estimate the amount of force needed to actuate the clutch, and thus estimate the current needed to only actuate the motor as much as needed, so the system is appropriate sized and operating efficiently.